Method and apparatus for forming corrugated tubes, especially for making gaskets, and the product thereof



Feb. 5, 1963 H G JOHNSON 3,076,228

METHOD AND APPARATUS FOR. FOIMING CORRUGATED TUBES, ESPECIALLY FOR MAKING GASKETS, AND THE PRODUCT THEREOF HWENTOR. Herbert 6. Johnsan Feb. 5, 1963 H. s. JoHNsoN 3,076,228

METHOD AND APPARATUS FOR FORMING CORRUGATED TUBES, PECIALLY GAsxETs, AND THE PRODUCT THEREOF FOR MAKING Filed NOV. '7, 1960 2 Sheets-Sheet 2 HVVHVTOR. Harter! 6. Johnson 3,076,223. METHODAND APPARATUS FOR FORMING CDR- Ruos'run TUBES; ESPECIALLY ron4 MAKING? GASKETSIANDTHEPRDUCT THEREQF i T hispinvention relates `to method and apparatus for forming corrugated tubes, especially for-making'sheathed gaskets, `and'fto the productthereof; Land ha's.for"iar1' object the provision of :improvements-in this art.` l

One of the particular objects of fthe invention is to provide a simple and inexpensive method `form'aking multi-ply gaskets withfa sheath-protectdcorer i?" `Another object is to provide sim'ple `and-inexpensive apparatus' for 'making multi-ply andsheathed gaskets; provide `an improved 'type of Another object is'to sheathed core gasket.

Another object is to vprovide a simple and convenientl assembly forforming a corrugated `r tube with heat and: for quickly removing-the assembly with the `formed tube and quenching it.`

The above and Aother objects and advantages of the invention' will be'apparent `from the followingk descrip tion of an exemplary embodiment, reference being madey to the accompanying drawingsywhere'in:

FI ,G 1 is a longitudinal section through apparatus for forming a corrugatedtubeand gasket, the parts being' shown in the initial stage in which'a" tube and other elements have just been s'et un inthe machine;` 'Y

Frog Vis a View ure FIG; 1 `but showing, 'a later stage of operations;

FIG.V 3 risi-a view like FIG. 1 but shwing a sau" later stage of operations;

FIG. 4 is a section through the formed assembly removed from the machine after another operation has been performed bythe machine;

FIGQS-is a section"1ike"`FIG. 4 tion has been performed;"and

FIG. 6` is asimilarsection after the final operation.

The invention can be used'for'making'gaskets o'f`various lmaterials lfor-various Yusesbutis believed `tohave special advantages'formaking -gaskets, which are sheathed with materials which arerhighly resistant 'to most harm"- ful agents encountered'in'thenewartsof nuclear rea'c` tions and thei'likew-Oneofv thel-be'st materials'presently used for resisting attack is polytetraiiuoroethylene (PTFE, usually referred to by the trade name Telion). Others of a similar nature, such as Kel-F and the like, are known.

The present method of making a sheathed core gasket of PTFE, so far as known, is to machine out a solid rod or thick-walled tube of PTFE to form spaces for cores, put in the cores, and secure them in the sheath thus formed. This procedure is slow and intricate and very wasteful of extremely expensive material.

'Ille present invention requires only a simple tube 10, FIG. l, which is placed on a mandrel 11 having a Huid duct 12 with ports 13 for supplying pressure liuid to the interior of the tube.

A plurality of die elements 1S, 16, 17, 18 and 19 cooperate with the mandrel to form corrugations a on the tube, as shown in FIG. 2.

The base die member 15 may be secured to the base 11a of the mandrel, as by welding 2l), and the die member has an annular groove carrying a seal 21, such as a rubber O-ring, which forms a fluid-tight connection when uid under pressure is present in the tube. The tube end is easily pushed in past the ring when no pressure fluid ,after `another operas present and can readily be pulled out under the same conditions; i l i f Afsimilar seal 22 19 and the mandrel. will-beissen 'that'the mandrel slides past the seal 23 during a corrugatingtaction.

base end of the mandrel. along the-mandrel it-would be 'necessary to provide'a sealed enclosure on `the outer end of the-die e1em'ent19 toreceive the `end of the'mandrel to prevent loss of:

fluid.

The intermediate die elementsl16, 17 and 18 are formed in a 4plurality--of circumferentially extending axially divided parts which are held' together in use either by powers` means (forl a ful-lymechanized press) or by connecting automatic arrange-r means such as bolts 25 (for a less ment).

The intermediate die elements 16,

die elementsfl', 19 arelplaced on the tube and before the divided die elements 16, 17, 13 are put on the cores- This may;A be of any material'desiredfor a gasket core. lPreferably* and-their parts-secured together on the cores.

it is resilient, as of cork, rubber, asbestos, or the like. By. forcing the `die elementsaxially vtogether in a press while fluid pressure is provided in the mandrel, the cor-t rugationsflia'are formed on the tube. For materials which need it, the mandrel is provided with heating means 27, here lshown a-s an electric heater with conductorleads extending out at the left end, as shown. PTFE and other plastics which have memory are specially benefited -by heating during formation and quenching after formation:

the cores so as to providematerial for enveloping the peripheries o'f the cores. Y t

,After the intermediate die elements 16, 17 and 18 have been 'removed'the end die elements 1'5 and 19 are' squeezed together axiallyto cause 'the corrugated tube to-closelyembracethecores,asshown in F1654;

The tube with the cores thereon and the end die element 19 can be quickly slipped oi the mandrel after the forming operation and with pressure o so the tube can be quenched to stabilize the final shape. Easy set-up and removal provide rapid operations.

Next, the crests of the corrugations are cut open circumferentially, as shown in FIG. 5, to leave each core and its cover separated from the others. Each envelope is U-shaped in its annular cross section. These U-shaped annular envelopes may be designated as 10b. The end edges which protrude beyond the core may be designated as llibl.

As shown in FIG. 6, these protruding end edges llibl are bent over the outer periphery of the core to fully cover it. The edges may be sealed together, as by heating to fuse them. When the gaskets are secured between parts in use it is not so essential that the outer edges be sealed together since the inner edge which encounters material inside a pipe is a continuous sheet. If the edges do not fuse together and are not readily joined by adhesive they may be held down by a band on the outer periphery.

Preferably the cores and finished sheathed gaskets are made to be slightly thicker axially at the inner radius than at the outer radius so that when squeezed between Patented Feb. 5, 1955i is provided inthe other end dievmem-I ber 19;` Ascal-23 isprovided 'betweenvr the diemember` By comparing FIGS. :l and 2, it

To avoid tiuid Ieakagewhen themandrelisl pushed out, thefports 13 are placed near the. If they should be placedv alli 17 and 18 are providedeach with an annular groove to receivel a core ring, 26. `VBy, ring is meant, as usual, an` endlessannular member which is threaded on the tube before the end# It. will'be notedithat the corrugations areA widerradially thanV amazes pipe flanges the tightening will begin at the inner radius and progress outwardly.

There is very little thinning of any part of the tubeA wall in this operation, suchthinning as there is coming at the outer periphery of the corrugations to leave unthinned the valleys which wrap the iner edges of the cores. This is an advantage also in leaving the core coverings thinner toward the radially outer edges.

t will be noted that the ends of the tube d are left without cores. These need not be wasted because there are many uses for an angular-section gasket such as these will make.

If it is desired to make gaskets without cores by this method the cores are omitted and intermediate dies without an annular groove are used. Then when they are removed the corrugations will be completely attened when pushed together.

1f it were desired, the cores could be omitted at the start and when the shape of FIG. 3 was reached the cores could be supplied, as by winding material in the valleys or by lilling them to the desired depth by fluent hardenable material. n

It is thus seen that the invention provides improved apparatus and method for forming corrugated tubes and making gaskets and also provides an improved gasket which can be made at a low cost.

While one embodiment of the invention has been described for purposes of illustration, it is to be understood that there may be various embodiments and modifications within the general scope of the invention.

I claim:

1. The method of corrugating tubes, as for making gaskets with a sheathed core, which comprises, placing an annular core on a tube to be expanded, placing axially divided annular die elements over and around said core, supporting and holding the tube on either side of the die elements and core at such distance as to provide corrugations on opposite sides of the core which will be radially as deep as the core, applying lluid pressure within the tube while compressing it axially to form corrugations on each side of the die elements and core, removing the divided die elements from the core, and squeezing the corrugated tube axially to closely envelop the core in the annular valley space between corrugations.

2. The method as set forth in claim 1, further characterized by the fact that enough length of tube is left on each side of the core to form corrugations which when llatened are radially of enough greater depth than the core to provide sutcient material in the valley space between the flattened corrugations to completely surround the core.

3. The method as set forth in claim 1, further characterized by the fact that die elements are used which are axially wider than said core, that said corrugations are flattened by axial pressure while said die elements are still in place on the core, and that the portions of the tube on the sides of the core are squeezed axially upon the core after the die elements have been removed.

4. The method as set forth in claim 1, further characterized by the fact that die elements are used which are radially wider than the corrugations to be formed and axially wider than said core, that said corrugations are flattened by axial pressure between die elements, and that the portions of the tube on the sides of the core are squeezed axialy upon the core after the die elements have been removed.

5. Apparatus for corrugating tubes, as for forming gaskets, comprising in combination, a plurality of tlatsided die elements surrounding a tube at axially spaced points therealong, one of said die elements including axially divided parts having an inner groove embracing an annular core on the tube, which core is axially narrower than said divided die elements, to form corrugations axially spaced away from the core, and said divided die elements being removable from the tube to leave the annular core thereon, means to supply fluid under pres-l f sure within the tube to form corrugations on it, means for moving said die elements axially to assist in forming corrugations and flattening them between the flat sides of the die elements, and also for squeezing the core between corrugations after the core-embracing die elements have been removed from the core.

6. Apparatus as set forth in claim 5, in which said divided die elements are radially wider than the corrugations which are formed, and said annular core being radially narrower than the corrugations which are formed.

References Cited in the tile of this patent 

1. THE METHOD OF CORRUGATING TUBES, AS FOR MAKING GASKETS WITH A SHEATHED CORE, WHICH COMPRISES, PLACING AN ANNULAR CORE ON A TUBE TO BE EXPANDED, PLACING AXIALLY DIVIDED ANNULAR DIE ELEMENTS OVER AND AROUND SAID CORE, SUPPORTING AND HOLDING THE TUBE ON EITHER SIDE OF THE DIE ELEMENTS AND CORE AT SUCH DISTANCE AS TO PROVIDE CORRUGATIONS ON OPPOSITE SIDES OF THE CORE WHICH WILL BE RADIALLY AS DEEP AS THE CORE, APPLYING FLUID PRESSURE WITHIN THE TUBE WHILE COMPRESSING IT AXIALLY TO FORM CORRUGATIONS ON EACH SIDE OF THE DIE ELEMENTS AND CORE, REMOVING THE DIVIDED DIE ELEMENTS FROM THE CORE, AND SQUEEZING THE CORRUGATED TUBE AXIALLY TO CLOSELY ENVELOP THE CORE IN THE ANNULAR VALLEY SPACE BETWEEN CORRUGATIONS. 